In hopes of obtaining a better understanding of the relationship between the steroidogenesis and the action of ACTH in adrenal cortex, we have been studying the molecular basis of the enzymes, proteins, and other factors in adrenal cortex, testis, and ovary. In extending this study, I propose works on (1) chemical and physical properties of adrenodoxin, (2) biosynthesis of iron-sulfur proteins, (3) lipid peroxidation and degradation of cytochrome P-450, and (4) properties of adrenodoxin reductase.